Release films with backing layers made of thermoplastics such as polyolefins, polyesters or polyamides and having a release layer based on a polysiloxane are widely used as protective films for adhesive tapes or self-adhesive labels, in order, for example, to prevent these single- or double-sidedly adhesive products from sticking during storage. Release films of these kinds are distinguished by a good release effect toward adhesives such as pressure-sensitive adhesives, for example, or other adhesive materials and also by good adhesion between the release layer and the backing layer. The adhesion of the release layer to the backing layer prevents at least partial, uncontrolled detachment (rub-off) of the release layer from the backing layer prior to the actual application.
A disadvantage of such release films, however, is that their backing layers are not biodegradable.
From both an environmental and an economic standpoint, however, it is desirable that at least the backing layers of such release films are produced from biodegradable materials, in order to ensure ultimate disposal of these materials by means of composting, for example, following controlled removal of the release layer.
There is therefore a need for predominantly biodegradable release films which in terms of their release effect meet the aforementioned requirements imposed on conventional release films, made from nonbiodegradable materials, and which, furthermore, also exhibit very good adhesion between backing layer and release layer.
It was an object of the present invention, therefore, to provide a release film which is predominantly—that is, more than 50%—biodegradable and which is distinguished by a very good release effect toward adhesives and adhesive materials in conjunction with excellent adhesion between the release layer and the backing layer without an adhesion promoter layer.